ES2840051T3 - Seed disinfection method - Google Patents

Abstract

A method for preparing disinfected seeds, comprising: - contacting the seeds for an exposure time of at least 10 seconds with a liquid treatment composition comprising water and one or more disinfecting agents selected from acetic acid, peroxyacetic acid, peroxide hydrogen, wherein any peroxide is present in an amount less than 20% by weight of the treatment composition; - and subsequently, exposing said seeds to a treatment atmosphere for an exposure time of at least 1 second, where the treatment atmosphere has a relative humidity of at least 50% and a temperature of at least 40 ° C.

Description

DESCRIPTION

Seed disinfection method

The invention relates to a method for preparing disinfected seeds, a use of a treatment composition and an apparatus for disinfecting seeds.

Disinfection or disinfection of plant seeds before planting is important to reduce the impact of seed-borne pathogens and improve crop yield and quality. In particular, it is desired to obtain better control of surface and internal bacteria. With current methods of seed disinfection, such control is difficult or impossible to obtain. Another wish is to reduce the use of harmful substances, such as some biocides, due to environmental and health concerns. Therefore, it is desirable to use smaller amounts and / or less harmful biocides.

International patent application WO-A-97/38734 refers to a heat treatment process for the disinfection of seeds from pathogens and other undesirable fungi and bacteria, which involves supplying the seeds with non-water-borne heat while they are regulates the time and temperature of the treatment with respect to the condition and moisture content of the seeds, in such a way that the seeds are heated from the outside while the moisture from the surface of the seeds evaporates and therefore cooling of the same is avoided and there are no changes in the moisture content. In the example, the degree of disinfection was determined based on the presence of pathogenic fungi. The method leaves scope for improving the disinfecting effect on seed-borne bacteria in various plant species.

Bang et al. (Food Microbiology, 2011,28, 114-118) describe a study on the combined effects of chlorine dioxide, drying and dry heat treatments on the inactivation of microorganisms in radish seeds.

Beuchat et al. (Journal of Applied Microbiology, 2002, 92, 382-395) describes a treatment of alfalfa seeds inoculated with Salmonella or E. coli that involves heating in water and chemical solutions, but no treatment in a humid atmosphere.

Forsberg, PhD thesis, 2004, Swedish University of Agricultural Sciences, Uppsala), deals with the treatment of cereal seeds using hot and humid air or aerated steam. The seeds are not contacted with a treatment composition comprising at least one disinfecting agent and / or a liquid component.

EP-A-2153876 describes an apparatus in which seeds are conveyed on a conveyor belt and sprayed with water in a first chamber and subjected to dry air in a subsequent chamber.

Document CN-A-203840725 refers to a sterilization and drying device for agricultural seeds, in which the seed is treated in three separate chambers.

Forsberg et al. (Zeitschrift für Pflanzenkrankheiten und Pflanzenschutz 2003, 110 (1), 1-16) describe trials in which cereal seeds are subjected to short treatments with hot and humid air. In this article we study the influence that the variable moisture content of the seed has on the heat tolerance of the seed.

An object of the present invention is to provide a method for preparing sanitized seeds that addresses one or more of the problems and desires mentioned above, at least in part. Surprisingly, it has been found that this objective can be achieved by contacting the seeds with a treatment composition in combination with exposing said seeds to a treatment atmosphere.

Accordingly, the invention relates in a first aspect to a method for preparing disinfected seeds, which comprises contacting the seeds for an exposure time of at least 10 seconds with a liquid treatment composition comprising water and one or more agents. disinfectants selected from acetic acid, peroxyacetic acid and hydrogen peroxide, wherein any peroxide is present in an amount less than 20% by weight of the treatment composition; and subsequently, exposing said seeds to a treatment atmosphere for an exposure time of at least 1 second, where the treatment atmosphere has a relative humidity of at least 50% and a temperature of at least 40 ° C.

The method advantageously provides improvements in the disinfection of bacteria seeds, especially seed-borne bacteria. Furthermore, the method makes it possible to use smaller amounts and / or less harmful substances, such as biocides. The method can further provide a disinfecting effect on seed-borne pathogenic fungi and other non-bacterial pathogens, eg seed-borne nematodes and insects. Furthermore, the method allows for seed disinfection without significantly affecting seed quality or germination properties.

The term "seed" as used herein includes, but is not limited to, a mature ovule of gymnosperms and angiosperms, which contains an embryo surrounded by a protective covering, the seed coat (testa). Some seeds comprise a pericarp or fruit layer around the seed coat. In terms For practical purposes, the term "seed" is the fertilized mature ovule of a growing plant that contains an embryo and is normally capable of germinating to produce a new plant.

The term "disinfection" of plant seeds includes, for example, eliminating, killing, rendering harmless and / or reducing the impact of a pathogen, in particular bacteria and fungi. Pathogens can also be seed-borne nematodes and insects, including their eggs. Preferably, the pathogens are bacteria. Rendering a pathogen harmless includes, for example, rendering the pathogen unable to infect the plant. Some examples of methods for preparing disinfected seeds include seed treatment methods that reduce the percentage of infected seeds and methods that reduce the number of colony-forming units.

The term "disinfection" is not used in the sense that it implies a restriction on the objects to be disinfected, in particular, the seed of the plant can be considered alive or non-living.

The term "disinfected seed" includes, and is not limited to, a seed for which a reduction in the number of infected seedlings and / or colony forming units is observed for one or more pathogens compared to untreated seed. Thus, a disinfected seed can still contain several live pathogens. An example of a disinfected seed is a seed in which the inoculum pathogenic for at least one type of pathogen is rendered at least partially harmless or less harmful, for example by killing, eliminating or inactivating it.

The term "disinfecting agent" refers to a compound or composition that exhibits a disinfecting effect.

The term "treatment atmosphere" as used herein includes a gaseous phase having a temperature and relative humidity to which the seed is exposed. The term "relative humidity", as used herein, refers to the relationship between the partial pressure of water vapor in the gas phase and the saturated vapor pressure of water at the temperature of the treatment atmosphere. The term "exposure time", as used herein, refers to the duration of exposure of the seed to the treatment atmosphere.

The term "dormancy" for bacteria includes at least a state of low biological activity, low metabolic activity, or rest. The term also includes a "viable but not arable" status. The term includes bacteria that do not grow and cannot be grown on standard media (eg agar), but still exhibit metabolic activity or the potential to show such activity later (resting stages), indicating that the bacteria are viable. Generally, favorable conditions can result in reactivation of bacteria. Such reactivation is sometimes called resuscitation.

In general, most commercial seeds are dried, for example, to an absolute moisture content of 4.5-8% (vegetables and flowers) and between 8-11% for agronomic seeds and tree seeds, and generally 10 -16% for cereals. The low moisture content in commercial seed is achieved by a drying procedure in the field or after harvest, which is often applied to ensure adequate seed life.

Bacteria may enter a dormant state and / or develop biofilm protection against environmental stresses, such as drying and low temperatures. Thus, the seed, whether dry or not, can contain seed-borne and / or seed-borne bacteria in a "dormant" state. Bacteria in this state may be less sensitive to environmental changes. For example, dormant bacteria can survive drastic environmental changes in temperature and pH or oxygen deprivation that would be lethal to non-dormant bacteria. As a result, general seed disinfection methods may be less effective against dormant bacteria than against active bacteria.

Without wishing to be bound by theory, the advantageous results of the combination of a treatment composition and a treatment atmosphere can be obtained at least in part by virtue of one or more of the following effects. For example, contacting a seed with a treatment composition can cause the reactivation of dormant bacteria. In this way, a subsequent exposure of the seed to a treatment atmosphere can be more effective, since there are fewer dormant bacteria during exposure to a treatment atmosphere. Similarly, a sanitizing agent may be more effective against active bacteria. Sanitizing agents that have a stronger sanitizing effect at higher temperatures, for example water and peroxides, can have a synergistic effect with the treatment atmosphere. Increasing the moisture content of pathogen cells can facilitate chemical and physical reactions, including reactions that impair pathogen functions.

Alternatively or in addition, a higher temperature during exposure of the bacteria to the treatment atmosphere can make the bacteria more susceptible to the action of a disinfecting agent. Alternatively or in addition, a sanitizing agent may be more active or effective at higher temperatures. Such a disinfecting agent can be applied to the seed by the treatment composition.

Alternatively or in addition, the treatment composition can mitigate the effect of air pockets on the endosperm of the seeds. Such air pockets can be formed by air trapped in (or between cell membranes) pockets in seeds, especially dry seeds. In addition, the pores of some seeds can provide air in intracellular spaces or air pockets. Since air is not a good conductor of heat, this It can help reduce the effect of exposure to the treatment atmosphere. The disinfecting efficacy of exposure to a treatment atmosphere can be increased by at least partially replacing the air in such air pockets and / or pores with a liquid treatment composition, particularly water, since liquids are better conductors of heat. This includes moistening such pores or pockets by the treatment composition. This can increase the rate of heat transmission within the endosperm and can also improve the effect against any bacteria located within the air pockets, reducing the time of exposure to heat of the embryo, which can be lethal. Filling or moistening of air pockets can also improve contact between a sanitizing agent and bacteria within such pores, increasing the effect of the sanitizing agent. To increase its effectiveness, the method preferably comprises shaking or vibrating the seed with the treatment composition (eg with ultrasound) during or after contact with the treatment composition.

Alternatively or in addition, contact with a treatment composition comprising a liquid component can result in wetting of the seed surface. This can help mitigate any insulating effects of the roughness of some seeds, which could otherwise limit the effectiveness of exposure to a treatment atmosphere. A treatment composition comprising a surfactant can provide improved wetting. A surfactant can also help deliver a sanitizing agent effectively to the endosperm of the seed. Seed wetting can further increase process control by delivering heat at a more constant temperature, and also for cooling after exposure to a treatment atmosphere. Sufficient and rapid cooling is important for seed quality and germination properties.

Regardless of the effects mentioned above, which do not limit the invention by way of theory, the examples demonstrate a synergistic effect of a treatment composition and a treatment atmosphere that results in more effective disinfection. Even with only water as the treatment composition, an advantageous interaction was demonstrated on exposure to a treatment atmosphere.

Accordingly, the seed may comprise dormant bacteria prior to contact with a treatment composition and, optionally, the seed is provided as dry seed. Preferably, the method comprises reactivating at least some dormant bacteria by contacting them with a treatment composition and / or exposing them to a treatment atmosphere, more preferably by the treatment composition. Preferably, the method comprises subjecting reactivated bacteria and / or other pathogens to a disinfecting agent and / or heat by exposing the seed to the treatment atmosphere. In such a preferred method, exposure to heat can have a disinfecting effect on reactivated pathogens as well as other sensitive pathogens.

The treatment composition comprises water. To improve wetting, the treatment composition preferably comprises a surfactant. This can also provide better penetration of the treatment composition into the seed into any air pockets and / or pores in the seed. Surfactants can also contribute to the shedding of bacteria from the seed, in particular where the bacteria adhere to the surface of the seed by hydrophobic interaction. This is especially advantageous for crops that have seeds with a hydrophobic seed surface. For example, some seeds have a surface that comprises epicutular waxes. Such waxes can comprise alkanes, long chain alcohols, ketones and / or long chain fatty acid esters. The seeds of some crops include hydrophobic proteins in their seed coats. Examples include soybeans and rapeseed. For such crops, a treatment composition comprising a surfactant is particularly advantageous.

Preferably, the seed is supplied with a liquid treatment composition comprising water and surfactant in an amount that provides at least 10 g of water per kg of seed and / or at a temperature of at least 20 ° C.

Preferably, the method involves wetting the seed by a liquid treatment composition and / or saturating at least part of the seed's intracellular space (pores) and / or air pockets with a liquid treatment composition. This can provide more efficient heat delivery to pathogens in these air pockets and pores, in view of the higher thermal conductivity of water and liquids compared to air. The filling of pores or air pockets can be determined, for example, by freezing followed by microscopy. Therefore, preferably, during exposure of the seed to a treatment atmosphere, the pores and / or pockets of the seed contain a liquid treatment composition, more preferably they are essentially filled with said composition. Preferably, the method comprises exposing the seed to a treatment atmosphere while the pores and / or bags of the seed contain a liquid treatment composition comprising water and one or more disinfecting agents selected from acetic acid, peroxyacetic acid and hydrogen peroxide. Preferably, the method comprises shaking or vibrating (eg with ultrasound) during or after contact with the treatment composition. This can provide, for example, greater efficiency of wetting the seed and / or filling or wetting the air pockets.

The seed to be disinfected is usually able to germinate. Suitable seeds include non-germinated, preferably non-primed seeds. Optionally, the seed can be deprived of the shell (dehulled seed or dehulled seed). Preferably, directly before contact with a treatment composition and / or exposure to the treatment atmosphere, the seeds have a temperature of -10 ° C to 30 ° C, more preferably 0-25 ° C, for example 10- 25 ° C, and optionally kept above 5 ° C, 10 ° C or 15 ° C during the method up to the optional cooling stage. Optionally, the method begins by opening a package containing seeds or by providing a batch of seeds. The method may also comprise providing seeds to a seed treatment unit prior to said contact, wherein the unit comprises, for example, a seed chamber with at least one inlet for the treatment composition. The method optionally comprises recycling the treatment composition. The seed, as supplied, may comprise seed-borne pathogens, such as bacteria, particularly dormant bacteria, or it may be susceptible or at risk of containing such bacteria.

The method involves contacting the seed with the treatment composition. Preferably, the contacting with the treatment composition is carried out at least in part at a temperature of less than 50 ° C or less than 40 ° C, such as 5-50 ° C. Preferably, during contact, the seed and / or treatment composition has a temperature of less than 50 ° C or less than 40 ° C, such as 5-50 ° C, most preferably 15-35 ° C. Preferably, the treatment composition is applied at a controlled temperature. This advantageously provides high efficiency and / or reliability. Preferably, the treatment composition is applied at least 15 ° C or at least 20 ° C. The seed is contacted with the treatment composition for a contact time of at least 10 seconds, such as at least 1 minute, or at least 5 minutes or at least 10 minutes, and for example less than 24 hours, such as less than 60 minutes, for example 10-30 minutes or 60-300 seconds. The seed can be contacted with the treatment composition, for example, by soaking or dipping the seed in the treatment composition, or by spraying, dripping or flowing the treatment composition on the seed, or by a controlled increase in humidity, condensation , soaking, or washing the seed with the seed treatment composition. For example, a gaseous treatment composition can be blown onto the seed. For example, a powdered treatment composition can be mixed with the seed.

Optionally, the seed can be provided in a bag or basket, on a plate, or in another form of container during contact, and also on a moving belt. The method can optionally result in absorption of the treatment composition by the seed. The absorption of the treatment composition into the seed can provide improved antimicrobial efficacy, especially against internal bacteria. Preferably, the weight of the seed increases during contact with the treatment composition by at least 1.0%, based on the difference in the weight of the seed before and after said contact, with the removal of the excess composition of treatment, divided by weight before contact. Removal of excess treatment composition may involve, for example, drying the seed with a cloth. The weight gain can be, for example, 0.10-25%, such as at least 1.0%, at least 2.0%, for example less than 20%, for example 2-15% and / or 15 -25%. Thus, the seed can absorb the treatment composition in an amount of, for example, at least 5% or at least 10% of its weight, such as 15-25% or 20-25%.

Contact can also result in some swelling of the seed, for example a volume increase of at least 0.5% or at least 2.0%.

The method comprises exposing the seed to the treatment atmosphere, after contact of the seed with the treatment composition.

In principle, the method may comprise two or more steps of contacting a treatment composition, wherein the treatment composition can be the same or different. The method may also comprise any additional step of contacting seeds with compositions at any step of the method, either with treatment compositions that have the same or different disinfecting agent and / or liquid component, or with compositions that do not comprise a disinfecting agent. no liquid component.

Preferably, the method comprises removing at least part of the treatment composition from the seed prior to exposure to a treatment atmosphere. For example, the method may comprise removing excess treatment composition. This is especially advantageous in case the treatment composition is phytotoxic. Removal of the treatment composition may comprise centrifugation, evaporative drying, eg, touch-drying (eg, gently drying with a towel or similar cloth), wiping, blowing, and wringing by gravity or pumping. Removal may comprise, for example, rinsing (preferably with water). For example, the method may comprise rinsing with water for 10 seconds to 10 minutes. The seeds can also be centrifuged, for example, for 10 seconds to 5 minutes, optionally in combination with rinsing.

The treatment composition comprises at least one sanitizing agent and a liquid component comprising water, and may comprise additional components. The liquid component is preferably water. For example, the treatment composition can consist essentially of water (such as greater than 99% by weight), for example, it can be tap water. Thus, the method may comprise contacting the seed with water.

The treatment composition is a liquid aqueous composition, for example: a solution, suspension, dispersion, emulsion or foam, and also as a spray, mist or aerosol. Preferably, the treatment composition comprises a surfactant.

The surfactant can improve the effectiveness of hydrophobic disinfecting agents by improving the contact between such agents and bacteria.

For example, anionic, cationic, zwitterionic and nonionic surfactants can be used. Preferably the surfactant is an organic compound comprising a hydrophilic group. Examples include linear alkylbenzenesulfonates, lignin sulfonates, fatty alcohol ethoxylates, and alkylphenol ethoxylates. Some possible surfactants have anionic functional groups such as sulfate, sulfonate, phosphate and carboxylates, in particular alkyl carboxylates, for example dodecyl sulfate salts and alkyl ethers thereof. Cationic surfactants include primary, secondary or tertiary amines and quaternary ammonium salts, in particular aromatic quaternary ammonium salts. Other surfactants are zwitterionic compounds that have a phosphate anion with amine or ammonium. Polyoxyethylene and polyoxypropylene glycol alkyl ethers can be used, as well as, for example, glycoside alkyl ethers, glycerol alkyl ethers, polysorbate, block copolymers of polyethylene glycol and polypropylene glycol and polyethoxylated tallow amine. The skilled person can apply suitable amounts of surfactant, such as at least 1 ppb or at least 10 ppb (parts per billion by weight) or at least 100 ppb or at least 1.0 ppm, at least 10 ppm, to the less 20 ppm (parts per million by weight), at least 0.010% by weight, at least 0.10% by weight, at least 1.0% by weight, based on the total weight of the treatment composition, or for example concentrations providing at least 1 pm or at least 1 mg or at least 10 mg, at least 0.10 g, at least 1.0 g, at least 5.0 g or at least 10 g per kg of seed.

Preferably, the treatment composition comprises rhamnolipids. These can act as surfactants. For example, glycolipids having a glycosyl head, a rhamnose residue and a fatty acid tail such as a 3- (hydroxyalkanoyloxy) alkanoic acid (HAA) tail of fatty acid can be used. A concentration of, for example, between 10 ppb and 100 ppm, such as 1-100 ppm by weight can be used in the treatment composition, for example 0.0010-0.10 ml / l.

The seed is contacted with the treatment composition for at least 10 seconds, such as at least 30 seconds or at least 60 seconds. More preferably, the seed is in contact with the treatment composition for 10 minutes or more, such as 20-60 minutes or 20-40 minutes. It is preferred that the water has a temperature less than 50 ° C, more preferably less than 40 ° C, such as 20-40 ° C.

The seed is preferably wet at the beginning of exposure to the treatment atmosphere, and preferably comprises at least 0.10% water adhering to the seed, based on the total weight of the wet seed, more preferably at least 1.0% or at least 2%, generally less than 10%. The amount of water that adheres to the seed can be measured by removing it as is conventional, for example by gently wiping the seed to dry. Preferably the seed has a moisture content of at least 5% or at least 8%.

The liquid treatment composition comprises water and one or more sanitizing agents selected from acetic acid, peroxyacetic acid and hydrogen peroxide, wherein any peroxide is present in an amount less than 20% by weight of the treatment composition.

The treatment composition may comprise at least 0.010% or at least 0.10%, or at least 1.0% sanitizing agent, based on the total weight of the treatment composition. Preferably, a sanitizing agent is supplied to the seed in an amount of at least 10 mg or at least 1.0 g per kg of seed, such as at least 5 g per kg of seed.

Optionally, the treatment composition has a pH of less than 6, less than 5, or even less than 4, which contributes to the bactericidal effect.

A disinfecting agent preferably has low or no phytotoxicity in the amount applied, and is preferably non-persistent. Phytotoxicity is known for many commercially available agents, and can be tested according to routine methods. Optionally, the treatment composition can comprise, for example, seedling nutrients.

The treatment composition may comprise, for example, a peroxide compound such as hydrogen peroxide, for example at least 0.10%, at least 0.50% or at least 1.0% by total weight of the treatment composition. . The composition contains less than 20% by weight of peroxide and preferably less than 5.0% by weight, in view of the effect on germination properties. Suitable commercial peroxide solutions are available. The peroxide solution may contain the usual stabilizers for peroxide as appropriate. The composition is an aqueous solution, and may further comprise an organic acid, such as peracetic acid and / or acetic acid, and / or a surfactant. The treatment composition may comprise, for example, peracetic acid and hydrogen peroxide in a mass ratio of 2: 1 to 1:10, preferably 1: 1 to 1: 5, more preferably 1: 1.2 to 1: 4 and further optionally comprising a surfactant and / or solubilizing agent, preferably with a hydrogen peroxide concentration of 1.0-10% by weight, more preferably 2.0-7.0% by weight.

The treatment composition is preferably supplied to the seed in an amount of at least 0.1 g or at least 1.0 g or at least 10 g or at least 0.1 kg of seed per kg of treatment composition.

The treatment composition comprises water and is supplied to the seed in an amount that provides at least 100 g of water per kg of seed, or at least 1.0 kg of water per kg of seed, such as at least 2 kg of water. or at least 5 kg of water per kg of seed. For example, the seed can be soaked in the treatment composition in a ratio of at least 5 parts of liquid to 1 part of seed, or at least 10 parts of liquid, by weight. In a continuous procedure, the ratio is applied to the amount of water and seeds delivered per minute.

Contacting the seed with the treatment composition can result in an increase in the moisture content of the seed. For example, the moisture content of the seed can be increased by 5% or more, such as 10% or more, or 20% or more.

According to the invention, the seed is exposed to the treatment atmosphere after contacting the seed with the treatment composition. It is preferred that the seed is exposed to the treatment atmosphere 30 minutes or less after the seed has been contacted with the treatment composition, such as 15 minutes or less, preferably 10 minutes or less, more preferably 1-5 minutes.

The method comprises exposing the seed to a treatment atmosphere for at least 1 second, where the treatment atmosphere has a relative humidity and temperature. The treatment atmosphere has a relative humidity of at least 50% and a temperature of at least 40 ° C.

Preferably, the treatment atmosphere has a relative humidity of at least 60%, more preferably at least 70%, even more preferably at least 80% or at least 90%. Preferably, the treatment atmosphere has a relative humidity of 100% or less. The use of a treatment atmosphere with such relative humidity allows to advantageously reduce the amount of evaporation from the seed during processing. In some respects, it enhances some controlled water absorption which can take place directly from steam or from a thin layer of condensed water on the surface of the seed.

The treatment atmosphere can be saturated or supersaturated with water vapor. Optionally, the treatment atmosphere can comprise superheated steam. The treatment atmosphere preferably comprises a mixture of air and steam. The treatment atmosphere can be prepared, for example, by mixing air and steam, and is provided, for example, in the form of a stationary or fluid gas phase, preferably a gas stream, comprising, for example, air and steam.

The treatment atmosphere can reach a relative humidity of for example 100%, at least in parts of the seedbed. The method may comprise, for example, transferring heat from the steam contained in the treatment atmosphere to the seed. The method optionally comprises condensing water vapor from the treatment atmosphere on the seed, for example temporary condensation. This can advantageously contribute to efficient heat transfer to the seed. Condensation can result in the formation of a thin liquid film of water on the seed. The film can, for example, be absorbed onto the surface of the seed in a controlled way. The method optionally comprises evaporating said thin liquid film of water during the preferred cooling phase and optionally drying. The method can also optionally comprise the direct transfer of heat and moisture from the air to the seed, without water condensation.

Without wishing to be bound by theory, the formation of a thin liquid film of water can contribute to the effect of the treatment composition and / or the disinfecting agent it contains. In particular, the film can ensure that the components of the treatment composition remain on the seed and / or within the seed, for example in the thin liquid film, and / or below the surface of the seed. Evaporation and removal of components can be reduced by a thin liquid film and / or moisture. A higher temperature can contribute to the activity of a bactericidal and / or bacteriostatic component, such as a peroxide compound.

Optionally, the treatment composition is present on and in the seed during at least part of said exposure to said treatment atmosphere in an amount of at least 1.0 g of treatment composition per kg of seed, such as at least 10 g per kg of seed. For example, the seed may comprise at least 0.10 g or at least 1.0 g or at least 10 g or at least 50 g of disinfecting agent per kg of seed during exposure to a treatment atmosphere. Amounts include absorbed treatment composition. This can provide a beneficial effect of the treatment atmosphere on the effectiveness of the sanitizing agent.

Preferably, the disinfecting agent exhibits bactericidal and / or bacteriostatic activity, during said exposure to a treatment atmosphere, preferably bactericidal activity. Also in this way, the combination of contact with a treatment composition and exposure to a treatment atmosphere can contribute to an improved effect against bacteria.

Optionally, the treatment atmosphere comprises a sanitizing agent, preferably a vapor, mist and / or spray of a sanitizing agent. For example, hydrogen peroxide vapor or mist may be supplied to the seed during such exposure. Natural oils and volatile natural disinfectants, such as tea tree oil, can also be added.

Preferably, the treatment atmosphere to which the seed is exposed has a temperature of at least 50 ° C or at least 55 ° C, or even at least 80 ° C, typically less than 100 ° C or less than 85 ° C. Temperatures higher than 100 ° C are also possible, for example in combination with pressures higher than 100 kPa (1 bar), for example at least 110 kPa (1.1 bar), at least 150 kPa (1.5 bar), at minus 200 kPa (2 bar) or at least 500 kPa (5 bar).

Preferably, the temperature and / or the dew point temperature of the treatment atmosphere are kept substantially constant, for example, within a range of ± 5 ° C (increase or decrease of each not greater than 5 ° C, wide total 10 ° C), more preferably ± 2 ° C or ± 1 ° C or narrower, even more preferably in a range of ± 0.5 ° C, during said exposure to a treatment atmosphere.

Preferably, the exposure time, and therefore the duration of a stage of exposure of the seed to the treatment atmosphere, is 300 minutes or less, or 120 minutes or less, more preferably 30 minutes or less, 20 minutes or less, or 10 minutes or less. Some examples of non-limiting exposure times are at least 1 second or at least 10 seconds, for example 10 seconds to 10 minutes, or 30-300 seconds, or 60-300 seconds, or 90-180 seconds. Preferably, the seed is continuously exposed to a treatment atmosphere during said period. Another preferred method comprises a pulsed exposure to the treatment atmosphere, comprising at least two, such as at least three or four or five or ten or more exposures to said treatment atmosphere, for example each from 1 to 60 seconds, interspersed with exposures to colder atmospheres, for example, for 1-60 seconds. Such pulsed exposure can be carried out, for example, by alternating cooling and heating. Preferably, the treatment atmosphere comprises a gas stream, having a flow rate between 0 and 5 m / s just before and / or after a seed layer, for example 0.5-3 m / s or 1.0-2 , 5 m / s.

Optionally, the method for preparing disinfectant seeds comprises a batch process and / or a (semi) continuous process for exposure to the treatment atmosphere. In a batch process, the seed is preferably provided in a processing chamber, and the exposure of the seed to the treatment atmosphere preferably comprises introducing a treatment atmosphere into the processing chamber in which the seed is present. The batch treatment chamber is preferably a closed container with injection of humid air or steam before, after or simultaneously with the introduction of the seeds. Another preferred chamber is an open vessel where the treatment gas flows through the vessel from an inlet to an outlet. The container is preferably equipped with a mixing device or arrangement that can move around seeds and gas for greater uniformity. Exposure preferably takes place during fluidization of the seeds, therefore in a fluidized bed. Another preferred seedbed is a thin-set fixed bed.

In a continuous process, exposure of the seed to the treatment atmosphere is preferably carried out by moving the seed over a bed of seeds through a processing chamber comprising the treatment atmosphere. The movement of the seeds can be carried out, for example, by pneumatic transport, by gravity transport, by fluidization or by mechanical transport (for example, an endless screw, a shaking / vibrating conveyor, chain conveyor, belt conveyor or a rotating drum or elevator) or a combination thereof. The duration of exposure of the seed to the treatment atmosphere is typically equal to the residence time of the seed in the processing chamber, and can be controlled, for example, through the speed of a moving seed bed, such as as a chain conveyor through the processing chamber.

Generally, the seed is uniformly exposed to the treatment atmosphere. Preferably, the surface of the seed is uniformly exposed such that generally all parts of the surface of a seed are exposed to the treatment atmosphere for substantially the same time. In a continuous process, the seed is preferably exposed to the treatment atmosphere while the seed is on or in a vibratory fluidized continuous bed. The conveying speed is generally controlled by a built-in chain conveyor. Furthermore, the seed can be provided as a layer on a bed of moving seeds, wherein a stream of treatment gas as a treatment atmosphere can be blown from below through the bed of moving seeds into a processing chamber.

To increase energy efficiency, preferably the exposure to a treatment atmosphere is carried out in a system that is closed with respect to a gas stream, preferably by recirculating the treatment atmosphere in a closed circuit. In addition, the gas stream used for preferred cooling and / or drying can be recirculated to recover some of the heating energy, potentially combined with an air moisture trap to reduce air humidity. Preferably, the heating energy can also be recovered by heat exchange between an inlet channel for the treatment atmosphere and the exhaust gas.

Preferably, the treatment atmosphere has one or more, preferably all, of: a temperature of 50-100 ° C; a relative humidity of at least 75% and an exposure time of 1 second to 10 minutes, preferably 5 to 300 seconds.

For cereals, many seeds of vegetables, rice and other crops, the treatment atmosphere preferably has a temperature of 50-95 ° C, more preferably 55-80 ° C, most preferably in combination with a relative humidity of 70-100%, more preferably 80-100%, even more preferably 90-100%; most preferably in combination with an exposure time of 30 to 600 seconds, more preferably 60 to 300 seconds. An exposure time of 2-5 minutes, for example about 2 minutes (60-180 seconds), is preferably used in combination with a treatment atmosphere of 55-80 ° C, for example for cereals and vegetable seeds. For alfalfa seed and other more heat tolerant species, the temperature is preferably at the range of 60-90 ° C, preferably in combination with the same relative humidity and preferred exposure times.

Preferably, the seed has a core temperature of 20-50 ° C for at least part of the exposure time, preferably at the end of the exposure time. Preferably, the temperature in the core of the seeds is kept below 90 ° C throughout the exposure and / or disinfection method, more preferably below 70 ° C or below 50 ° C, to ensure good quality. of the seed. Preferably, the water content of the seed changes, preferably increases, during the exposure time by less than 10% by weight, based on the weight of the seed before exposure, more preferably by 1-5% by weight. Optionally, the water content does not change substantially. A limited change in water content can provide advantages, for example providing better germination or breaking seed dormancy.

In an advantageous embodiment, the method comprises contacting the seed with said treatment composition prior to said exposure, and the treatment composition comprises an aqueous solution comprising a surfactant, at least 0.10% by weight of acetic acid and al minus 0.10% by weight of one or more peroxide compounds selected from peroxyacetic acid and hydrogen peroxide, based on the total weight of the treatment composition. Preferably, in such a preferred method, the treatment atmosphere has a temperature of 50-100 ° C and a relative humidity of at least 80%, and the exposure time is 30 seconds to 10 minutes. Contact with the treatment composition is preferably carried out at 15-25 ° C and / or lasts for 60 to 300 seconds, for example 60 to 180 seconds, for example by soaking, optionally followed by rinsing with water, for example for 10-300 seconds. The seed can be centrifuged, for example, for 10-60 seconds and then exposed to a treatment atmosphere. The aqueous solution, for example, has a pH of 6 or less.

The seed is, for example, a seed of an agricultural crop that includes vegetables. Some examples of suitable seeds further include vegetable seeds, herb seeds, wild flower seeds, ornamental seeds and grass seeds, and tree and shrub seeds. The seed can be of the order of Monocotyledoneae or of the order of Dicotyledoneae. Some examples of the order Monocotyledoneae are rice and wheat seeds, Triticum aestivum. Some examples of suitable seeds include soybeans, cotton, corn, peanuts, corn, wheat, barley, oats, rye, triticale, mustard, sunflower, sugar beet, safflower, millet, chicory, flax, rapeseed, buckwheat, tobacco, Hemp seed, alfalfa, signal grass, clover, sorghum, chickpea, beans, peas, lamb's lettuce (Valerianella locusta) and pea. Some examples of suitable vegetable seeds include asparagus, chives, celery, leeks, garlic, beet root, spinach, beets, kale, cauliflower, sprouted broccoli, savoy cabbage, white cabbage, red cabbage, kohlrabi, bok choy, turnip , endive, chicory, watermelon, melon, cucumber, pickle, marrow, parsley, fennel, pea, beans, radish, black salsify, eggplant, sweet corn, popcorn, carrot, onion, tomato, pepper, lettuce, green beans, Cucurbits, Shallots, Broccoli, Brassica, and Brussels Sprouts. Some examples of rice include Oryza sativa japonica, Oryza glaberrima javanica, Oryza sativa indica, Zizania palustris, and hybrids thereof. The method is not limited to these example cultures.

Optionally, the method comprises, after exposure to the treatment atmosphere, one or more selected from the group consisting of: cooling, drying and removing the seed from a chamber or apparatus in which the seed is located, packaging the seed, for example in a bag or container, storing the disinfected seed, optionally at 2-10 ° C, coating or pelleting the seed, preferably by film coating, applying phytosanitary products and other additives on the disinfected seed, planting or sowing the seed in the soil or in a substrate and plants growing from said seed.

The method, for example, may comprise a further step of removing the cooled and optionally dried seeds from the processing chamber or from a cooling and / or drying chamber. The method further comprises, optionally, packaging the seed, for example, in a bag or container. The method may further comprise storing the treated seed, optionally at 2-10 ° C. Possible additional steps are sowing or planting the disinfected seed, germinating the seed, and growing plants from said seed, as a way to benefit from the disinfection effect.

The method preferably comprises cooling and optionally drying the seed after exposure to the treatment atmosphere. Drying can be carried out, for example, for a time period of 2-8 hours, such as 3-6 hours, preferably 4-6 hours. This cooling and drying comprises, for example, exposing the seed to a cooling and drying atmosphere. The cooling atmosphere and the drying atmosphere can be the same or different. Drying and cooling can be carried out successively or partially or completely simultaneously with each other. Preferably, the method comprises a combined cooling and drying stage and a subsequent cooling stage. Combined cooling and drying, for example, comprises exposing the seed to a drying atmosphere, typically with a relative humidity of 50% or less, more preferably 20% or less, and a temperature below the treatment temperature. but higher than ambient, typically 30-45 ° C. The drying atmosphere is typically air. The final cooling step typically comprises exposing the seed to an atmosphere with a temperature of 30 ° C or less, preferably no more than 5 ° C above room temperature, or around room temperature, but more preferably more. low, for example 10 ° C lower than ambient temperature. The cooling step preferably comprises exposing the seed to ambient air or air cooled to typically 10-25 ° C. Such a final cooling stage can also be applied without a combined cooling / drying stage. The seed is cooled, for example, at room temperature, or less than 5 ° C above room temperature, or up to storage temperature. The cooling phase is preferably carried out directly after exposure of the seed to the treatment atmosphere. Preferably, the cooling is carried out at least in part with a cooling rate of at least 5 ° C / min, such as at least 10 ° C / min; for example, in an initial cooling stage of 5-20 ° C in 1 minute or less.

Preferably, the cooling phase comprises exposing the seed to an atmosphere having a temperature of 45 ° C or less, in particular when the treatment atmosphere has a temperature of at least 50 ° C. Optionally, the end of the exposure to the treatment atmosphere is determined by the start of an exposure of the seed to a different atmosphere having a temperature of up to 45 ° C and / or a relative humidity of 45% or less. In the case of a batch treatment, the cooling optionally takes place in the same chamber in which the treatment takes place, or in two or more different chambers. Optionally, at least the last parts of the drying and cooling phase take place in a silo, container or an external dryer or refrigerator.

The method optionally includes pelleting or coating disinfected seeds obtained after exposure to the preferred treatment and / or cooling atmosphere and optional drying. Such a coating can, for example, protect the seeds from damage or can reduce dust or can improve plantability by increasing flow characteristics. Advantageously, the coating may comprise one or more active ingredients, such as plant enhancing agents and / or plant protection products (PPP), for example one or more selected from the group consisting of biocides, antimicrobial agent, fungicides, bactericides, insecticides. , nematicides, molluscicides, acaricides, acaricides, herbicides, rodenticides, pesticides, attractants, repellants, plant growth regulators, micronutrients, nutrients, minerals (such as potassium nitrate, magnesium sulfate, iron chelate), plant hormones , germination stimulants, pheromones, chitosan, chitin-based preparations. Coating preferably involves film coating or granulation. The film coating typically comprises a polymeric binder. Optionally, the seed comprises a coating composition as described in international patent application WO-A-2011/028115.

The method may optionally further involve a priming step, for example osmotic priming, hydropriming, solid matrix priming and / or drum priming, for example before contact with a treatment composition or after exposure to a treatment atmosphere.

The invention also relates to the use of a treatment atmosphere or gaseous composition having a relative humidity of at least 50% and a temperature of at least 40 ° C to improve the efficacy, in particular bactericidal and / or bacteriostatic, of an agent. disinfectant applied to plant seeds, in particular against seed-borne pathogens such as bacteria, especially against internal bacteria. Preferably, the atmosphere or gaseous composition used has a relative humidity and a temperature as described above, for example 50-100 ° C and at least 90%. Preferably, the use is to reactivate bacteria in said plant seed prior to exposure of the seed to said treatment atmosphere, wherein said treatment composition preferably comprises a surfactant and / or carboxylic acid.

Another aspect of the invention relates to the use of a composition comprising liquid water as defined above to improve the disinfecting efficacy of a treatment atmosphere, as described, to which said plant seed is exposed.

The methods of the invention can be carried out on numerous types of equipment, for example, as a batch or continuous process.

An example of an apparatus for carrying out the method as a continuous process comprises at least two chambers and conveying means for transporting seeds through said chambers, wherein a first chamber is suitable for bringing the plant seed into contact with the composition. aqueous treatment liquid, and where a second chamber is suitable to maintain a controlled atmosphere.

Preferably, the conveying means can continuously transport seeds through the chambers, such as pneumatic, gravity, fluidizing, and mechanical conveying means as described. The first chamber may comprise an inlet and an outlet for the liquid treatment composition, eg, a spray nozzle. The first chamber preferably comprises means for pouring / filling the liquid treatment composition and a metering unit and / or a valve for the liquid treatment composition.

The apparatus may comprise a solid-liquid separator between the first and second chambers to remove excess treatment composition, for example a centrifuge or screen. The apparatus may comprise a heating element in the second chamber or fluidly connected to the second chamber to provide heated vapor. The apparatus preferably comprises a third chamber for cooling and / or drying. A batch treatment can be carried out in separate chambers in which the seed is provided or in which a container containing the seed is provided, or in a single chamber capable of performing all the steps.

The invention further relates to a continuous process in which the seed is transported through a first chamber into the first chamber in which the seed is brought into contact for an exposure time of at least 10 seconds with a liquid treatment composition comprising water and one or more disinfecting agents selected from acetic acid, peroxyacetic acid, hydrogen peroxide, wherein any peroxide is present in an amount less than 20% by weight of the treatment composition, and said seed is subsequently transported through a second chamber in which second chamber the seed is exposed to a treatment atmosphere for an exposure time of at least 1 second, where the treatment atmosphere has a relative humidity of at least 50 % and a temperature of at least 402C.

The use of the terms "a" and "an" and "the or" and similar references in the context of the description of the invention (especially in the context of the claims) should be construed to cover both the singular and the plural, Unless otherwise stated herein or clearly contradicted by the context. The terms "comprising", "having", "including" and "containing" should be construed as open terms (ie, meaning "including, but not limited to") unless otherwise stated. The use of each and every example, or illustrative language (eg, "such as") provided herein, is merely intended to better illuminate the invention, and does not pose a limitation on the scope of the invention to unless otherwise claimed. No language in the specification should be construed to indicate any item not claimed as essential to the practice of the invention.

The invention will now be illustrated in more detail by the following non-limiting examples.

Examples

As a treatment composition, a commercial TC5 composition for horticultural disinfection was used comprising an aqueous solution of peracetic acid (5%) combined with hydrogen peroxide (20%). The contact of the seed with the composition of the treatment varies from 2 to 30 min depending on the solution. In some cases, the solution is removed or rinsed (1 to 5 min) with water to reduce toxicity after the exposure period. The seed can then be centrifuged or it can be directly subjected to the stage of exposure to the treatment atmosphere. Thereafter, the seeds are dried back to the original moisture content as much as necessary.

In all examples, GE is the germination energy (%), Germ is the final germination (%), TA is the treatment atmosphere, and TC is the treatment composition. Treatment compositions and surfactants used in the following examples are identified in Table 13.

Example 1

General bacteria were determined by planting the seed on a semi-selective medium (fungal growth inhibition) and incubated at 28 ° C in the dark. The counts were made at 4, 5 or 7 days and are presented as% of seeds infected with bacteria. A and B are comparative.

Table 1 shows the quality effect of the treatments on the onion seed. Values are the average of two standard tests of the International Seed Testing Association and are given as% germinated seed after 3 (EG) and 8 to 14 days (Final), both determined using 15 ° C in the dark with greenhouse test. Also shown is a value (% infected seed) for general surface bacteria (Gen. Bact.) Which was determined by planting the seed on a semi-selective medium (fungal growth suppressed) and incubated at 28 ° C in the dark. Counts were made at 5 and 7 days and were presented as a% of seeds infected with bacteria. The pretreatment was carried out with 5% by weight of TC5 (solution comprising 5% by weight of peracetic acid and 20% by weight of hydrogen peroxide, 20 times diluted). Sample C has fewer bacteria than comparative samples A and B.

Table 1

Example 2

In Example 2, Brassica seed was soaked for 2 minutes in 5% TC5, followed by a 1 minute rinse with water. The treatment atmosphere had 90% RH (relative humidity) and an exposure time of 2 minutes. Average results from 8 seed lots are shown in Table 2. Here GE day 5 is the emergence rate on day 5; Final GE is the final booth on day 7-8; Gen. Bact. general surface bacteria, as in example 1 on day 5; CD-48 refers to the 48 hour controlled deterioration or accelerated aging test evaluated on days 7-8; and mean CFU: mean Colony Forming Units of target pathogen per gram of seed, evaluated after 5 days on selective media.

Sample C shows that an improved bacterial reduction effect was obtained with CT compared to TA alone. The combination results in a significant reduction in general bacteria and the specific pathogen (Xcc = Xanthomonas campestris pv. Campestris) without significantly reducing germination values or CD values.

Table 2

Example 3

In Example 3, the method was applied to carrot varieties. The results shown in table 3 demonstrate the reduction of bacteria by exposure to the treatment atmosphere (90% RH, 2 min) in combination with contact with a treatment composition (2 min soak in TC5 (5% ), rinse with water 1 min, centrifugation for 30 seconds). CFU Xhc ( Xanthomonas hortorum pv. Carotae) was measured similarly to example 2.

Table 3

Example 4

In Example 4, the method was applied to Canon. The results are shown in table 4. A reduction of bacteria was obtained (in particular for foci of A. Valerianellae) by contacting with a treatment composition (2 min soaking in 5% TC5), followed by rinsing with water centrifugation for 1 min and 30 s and subsequent exposure for 2 min to a treatment atmosphere of 90% RH. Foci = number of seedlings infested with Acidovorax valerianellae in a group, measured according to ISTA 7-030.

Table 4

Example 5

In Example 5, the method was applied to watermelon varieties. The results given in table 5 demonstrate a reduction of bacteria, obtained by 2 min soaking in TC5 at 5%, rinsing with water for 1 min, centrifugation for 30 s and subsequent exposure for 2 min to a treatment atmosphere of 90 % RH. In particular, good results are obtained for the number of plants infected with Acidovorax citrulli.

Table 5

Example 6

In Example 6, the method was applied to carrot seeds infested with Xanthomonas spp. The results given in Table 6 demonstrate effective seed disinfection in combination with good germination properties. In particular, the use of water (tap water) as a treatment composition provides disinfection in combination with advantageous germination properties.

In all examples, N.d. indicates that a measurement was carried out but that the number of detected CFUs was below the minimum value or the detection limit of 100 CFU. The skilled person will understand that log CFU / 10,000 seeds refers in all examples to the common logarithm (base 10), such that a decrease with 1 indicates a 10-fold reduction in CFU.

Table 6

Example 7

In Example 7, the method was applied to Brassica seeds infested with Xanthomonas spp. and I would alternate. The results given in Table 7 demonstrate effective disinfection, in combination with good germination properties. In particular, good results were obtained for the loading of Xcc in batch 2, when comparing the treatment with and without the composition of the treatment.

Table 7

Example 8

In Example 8, the method was applied to Brassica seeds infested with Xanthomonas spp. The contact time with the treatment composition was 20 or 30 min, as indicated in tables 8 and 9, using the formulations and process conditions shown in table 10. The temperature of the treatment atmosphere was maintained the same for all samples (± 0.5 ° C) at temperatures above 50 ° C.

The results given in Tables 8 and 9 demonstrate effective disinfection, in combination with good germination properties.

Untreated sample 1 had a severe infestation. Sample 2 shows a reduction in bacteria by soaking in water followed by a 2 minute exposure to the treatment atmosphere. Sample 3 with a 3 min exposure time provided an even better reduction in Xcc. Treatment compositions comprising a surfactant yielded a lower amount of general bacteria. The amount of general bacteria was particularly low for samples 10 and 11, with a treatment composition comprising 0.2% H2O2 and acetic acid with 0.01% rhamnolipids. Table 9 shows that contact of the seed with the treatment composition for 30 minutes provides a good reduction in CFU of Xcc with various treatment compositions.

Table 8

Table 9

Example 9

In Example 9, rice seeds were soaked for 30 min in TC1 and TC2, followed by a 30 s centrifugation. The treatment atmosphere had 90% RH (relative humidity) and an exposure time of 2.5 min. The results are shown in Table 10.

Table 10

Example 10

In Example 10, Brassica seeds were soaked for 30 min in TC1 and TC2, followed by 30 s of centrifugation. The treatment atmosphere had 90% RH (relative humidity) and an exposure time of 2.5 min. The results are shown in Table 11.

Table 11

Example 11

In Example 11, Brassica seeds were soaked for 30 min in TC1, followed by 30 s of centrifugation. The treatment atmosphere had 90% RH (relative humidity) and an exposure time of 2.5 min. Average results from 19 batches of Brassica are shown in Table 12.

Table 12

Table 13

Claims (15)

1. A method of preparing disinfected seeds, comprising: - contacting the seeds for an exposure time of at least 10 seconds with a liquid treatment composition comprising water and one or more disinfecting agents selected from acetic acid, peroxyacetic acid, hydrogen peroxide, where any peroxide is present in an amount less than 20% by weight of the treatment composition; - and subsequently, exposing said seeds to a treatment atmosphere for an exposure time of at least 1 second, where the treatment atmosphere has a relative humidity of at least 50% and a temperature of at least 40 ° C. The method according to claim 1, wherein said treatment composition is supplied at a temperature of 15-40 ° C, preferably 20-38 ° C. The method according to claim 1 or 2, wherein said treatment composition further comprises a surfactant. The method according to any one of claims 1-3, wherein said treatment atmosphere has a temperature of 50-100 ° C and a relative humidity of at least 75%, and wherein said exposure time is up to 10 minutes . 5. The method according to any one of claims 1-4, wherein said treatment composition has a pH of 6 or less. The method according to any of claims 1-5, comprising contacting the seeds with said treatment composition prior to said exposure, wherein said treatment composition comprises an aqueous solution comprising a surfactant, at least 0.10 % by weight of acetic acid and at least 0.10% by weight of hydrogen peroxide, based on the total weight of the treatment composition, and wherein said treatment atmosphere has a temperature of 50-100 ° C and a humidity relative to at least 80%, and wherein said exposure time is 30 seconds to 10 minutes. The method according to any one of claims 1-6, wherein the treatment composition is supplied to the seeds in an amount of at least 0.1 g of seeds per kg of treatment composition, such as at least 1, 0 g, at least 10 g, or at least 0.1 kg of seeds per kg of treatment composition. The method according to any one of claims 1-7, wherein the treatment composition is supplied to the seeds in an amount that provides at least 100 g of water per kg of seeds, such as at least 1.0 kg of water, at least 2 kg of water or at least at least 5 kg of water per kg of seeds. The method according to any one of claims 1-8, wherein said seeds are exposed to the treatment atmosphere 24 hours or less after the seeds have been contacted with the treatment composition, such as 12 hours or less, preferably 6 hours or less, more preferably 2 hours or less, and even more preferably 1 hour or less. The method according to any one of claims 1-9, wherein the exposure to the treatment atmosphere is subsequent to the contact of the seeds with the treatment composition, and wherein the method comprises removing at least part of the composition from treatment of the seeds before said exposure. The method according to any one of claims 1-10, wherein the seeds are seeds of an agricultural crop. The method according to any one of claims 1-11, comprising, after said exposure to the treatment atmosphere, cooling and / or drying. The method according to any one of claims 1-12, comprising, after said exposure to the treatment atmosphere, coating or pelleting the disinfected seed, preferably by film coating. 14. Use of a treatment composition comprising water to improve the bactericidal and / or bacteriostatic efficacy of a treatment atmosphere having a relative humidity of at least 50% and a temperature of at least 40 ° C to which the substances are exposed. plant seeds for at least 1 second. 15. A continuous process wherein the seeds are transported through a first chamber, the first chamber in which the seeds are contacted for an exposure time of at least 10 seconds with a liquid treatment composition comprising water and a or more disinfecting agents selected from acetic acid, peroxyacetic acid, hydrogen peroxide, where any peroxide is present in an amount less than 20% by weight of the treatment composition, and said seeds are subsequently transported through a second chamber, a second chamber in which the seeds are exposed to a treatment atmosphere for an exposure time of at least 1 second, where the treatment atmosphere has a relative humidity of at least 50% and a temperature of at least 402C.